Variable-speed transmission



April '2, 1946.

Filed June 20, 1939 4 Sheets-Sheet l April 1946. D. P. FULLERTON, JR2,397,480

VARIABLE SPEED TRANSMISSION Filed June 20, 1959 4 Sheets-Sheet 2TI'ORNEY April 2, 1946.

D. P. FULLERTON, JR

F iled'June 20, 1939 4 Sheets-Sheet 3 6A 5 3 gw Dick P Flllerl? 052,

April 1946- D. P. FULLEl QTON, JR 2,397,480

VARIABLE- SPEED TRANSMISSION Filed June 20, 1959 4 Sheets-Sheet 0 DickPffilleronfi INV TOR a ORNEY Patented Apr. z, 1946 2,391.4VARIABLE-SPEED mnsmssron Dicks Phelps Fullerton. In, New York N. Y.

Application June 20, 1939-, Serial N0. 280.075

19Claime.

An object of this invention is to provide a variablespeedtransmissioniemploying a fluid flow variably controlled by theparticular requirements to'be met.

A further objct is to providea hydraulic torque converting mechanismhaving means enabling a full automatic control of the ratio of drivingto driven torque.

A further object is for controlling a variable speed transmissionemploying planetary gears. i

A further object is to provide improved means (ciao-es) I ure 1 showingthe gear-pumping mechanismoi,

topr'ovide improved means for controlling the flow of fluid in aplanetary gear type hydraulic tranmission.

A further object is to provide an improved hy-" dro-mechanical torqueconverter in which the ordinary hydraulic actions adequate to meetordinary operating conditions are supplemented by pulse action to meetextraordinary conditions.

A further object is to provide a hydro-mechanical torque converter inwhich the energy of the differential fluid is used'to produce additionaltorque. a v A further object is to provide a hydro-mechanicaltransmission in which the fluid flow tends to stabilize a direct drivebetween a driving and a larly suited for high torque driven shaft forall speeds of the driving shaft.

A further object is to provide a hydraulic torque converter in whichgearing, comprising a part of the transmissionralso propels or is pro--pelled by the fluid, the amount of fluid propelled or propelling beingautomatically variable in accordance with the and load.

' Still another object is to provide ahydraulic mechanism fortransmission of power in auto motive vehicles adapted for interpositionbetween obtaining conditions of powera driving and a driven member inwhich the flow of hydraulic medium is controlled so as to reslilate thetransmission between, as also the directionvof relative rotation of,member. with the hereinbefore mentioned objects. as also other objectsappearing from the specification, the invention comprises thecombination of elements and the details of construction hereinafter,respectively, claimed and described. it being understood that theinvention is notoonilned to the structures embodying the inventionherein described but solely as required by the scopeof the claims. I

4 In the accompanying drawings:

the driving and driven that embodiment; I v

Figure 3 a cross section on line 3-4 ot'Fisure 1 showing the hydraulicFigure 4 a simplified perspective, partially in section and exposed. ofthe pump and motor mechanisms of that embodiment;

Figure 6 a perspective, partially in. section and expmed, of the pumpeungear with its throttlin plungers employed in the-structure of Figure1;

' Figures 8A, 6B. 8C, and 7, schematic drawings for the purpose ofassisting in the un-- derstanding of my invention; and

Figure 8 still another'alternative form of my hydraulic transmissionempl y!!! aturbine. in longitudinal section.

- Figunes 1 to '5 inclusive disclose my invention incorporated in apower t nsmission primarily designed in automotive pE-qposes, andparticufor example, in truck and tractor applicatims.

Housing i is provided with shaft bearings I and 8 supporting.respectively, the driving shaft 4 and the driven shaft 5. Driving shaft4 is integral with the flywheel i and the pump planet housing 1.-Housing i completely encloses the pump planet and. motor planetmechanism which cou pics the driving and driven shafts, and is con-'-veniently aiiixed to the chassis of the motor vehicle. Driving shaft 4is propelledby .a prime r'nover (not shown), for example; the vusualinteriiai combustion-engine with variable fuel supply.

A plurality of planet gears l, for example-three,

are rotatably supportedwithin the pump cavity I. or thehousing fl, andmesh with sun gears, integral with driven shaft I.

.The pumpcavity Iii is so the planet gears l is within an-individualcylindrical portion or chamber ll thereof, each such portion. beingconcentric with its gear and connecting with the cylindrical chamber i2housing Figure 1 discloses a longitudinal section through one form of myhydraulic torque converter;

Figure 2 a cross section on line 2-2 oi Figs sun gear I and concentrictherewith. The cylindrical wall of chamber l2 has but a minimumclearance from the top or the teeth oi. sun gear 8 a so as to form aneffective hydraulic seal. For the reater portion i-i of theircircumferential extent, and on the intake sides 'of the planet gears,

the walls of chambers II are recessed to form a fluid passage around thetops of the planet gear teeth. The'intake side of each planet gearihasan individual series of fluid intake slots I I on individual intakelines II in the pump housing].

These slots are sealed from the pressure chamber of the pump it by theperipheral land it I motor mechanism of thatembodiment;

uirements; such as.

design ed that each of which extends a suii'lcient distance around the aplanet gear I so as to form continuously a hydraulic seal with one ormore of the planet gear teeth.

Each interstice between the teeth of sun gear 3 is connectedby aplurality of ports I! to an individual tubularbore It parallel to theaxis of rosulting force tending to force the slide valve 13 r to theright in the construction illustrated, The length of the slide valve l3between piston i6 and plunger I! is such that even when plunger llblocks the outlet bore 20, piston It does not interfere with ports l3,and when the valve I8 is in its extreme right position, at starting,plunger ll likewise does not interfere with ports l9. Obviously suchindividual bores, l5 and 20, parallel to the axis of rotation of thepump and motor sun gears and connecting from pump to motor, may also beprovided in the tooth portions of the gears, or may be there positionedalone, or spread along the length of the teeth, or may be in any desiredcombination of interstice and tooth position, just so long asappropriate valving is provided to prevent fluid from being sucked backfrom the bores l5 into the inlettinginterstices.

The automatic control valve is also housed within pump housing I, andcomprises a centrifugal flywelght' 22, or a plurality thereof, which, bythe action of gear 28 on the cylindrical rack 25, tends 1 to actuateinlet valve piston 23 on rotation. Valve head 29 of piston 23 normallyengages seat 30, thereby closing inlet passage or passages 2|. Piston 23is so constructed and mounted as to have its body engage housing I androtate therewith while capable of lateral displacement therein.

, Valve head 29 tends to remain in such seated position by spring .32tending to pull projection 3i mounted inpiston 23 to. the right. Theother end 33 of piston 23 is supported by thrust bearing 34. whichtransmits its lateral motion to plate 35, rotatable with, but laterallydisplaceable on, drivterstices and the succession of each pair relativeto the particular pair is the same, it is not necessary that the membersof the pair be in the same physical phase, Four channels 44, from thecavity 42, constitute selective exhaust ports and are positioned at thegear tooth intersection lines and are provided with individual controlvalves 45, 46, 41, and 43. The exhaust control valves are paired, sothat the upper left 46 and the lower right 48 are opened together, whilethe upper right 46 and lower left 41 are closed, and vice versa. Theyare operatable by the manual lever 43, accessible cutside casing l atsome place convenient to the open. Shaft. 5 Plate 35 imparts its lateralmotion to the slide valves It, to the piston ends l6 of which the plateis connected. The lower portion of the enclosing housing constitutes thesump 36, the suction tube 31 extending therefrom to the bearing supplygroove 38,'which in turn connects to the shaft inlet 21 and valve 29.

The hydraulic motormechanism is supported within housing I, at or nearthe driven shaft bearing 3. Sun pinion 33 is integral with the drivenshaft 5 and meshes with idler gears 40 and iii within the formed'gearcavity 42,- having at allpoints, but where ports are provided, a mini-.mum clearance from the top of the gear teeth and forming hydraulicseals. The inlet ports 43 at the interstices of the teeth of gear 39connect with the above mentioned tubular bores 20. I have shown,

erator. Lever 43 is rigidly connected to shaft 30, carrying gears ll and52, which, through gears 53 and 54, respectively, operate cam shafts 55and 53. Upper cam shaft 55 carries cams 51 and 58 so positioned thereonthat their throw occurs 180 apart. Similarly lower cam shaft 56 carriescams 39 and 33 similarly arranged, cam 59 being paired, as stated, withcam 53, and 60 with 81. Lever 49 is so arranged that it may remain inonly one of two positionsand never any other position driving position.This position is ordinarily the operation. The prime mover isthereuponstarted and the driving shaft 4 permitted to idle at slow speed. Underthese conditions flyweights 22 will not overcome bias spring 3! and theinlet valve cu remains closed. I Thus no fluid can flow and planet gears.3 idly roll over stationary sun gear 9. No power is thus transmittedand driven shaft 7 5 remains at rest. A I

To start the driven shaft .5, and thus the automotive vehicle,thedriving torque of the prime mover isincreased, for example, by supplyingmore fuel, i. e., opening the throttle. As the drive shaft 4 speeds up,the'flyweights 22 overcome the biasing spring 3!, moving piston 23 tothe left and opening valve. .As the pump planets .8 are rotating, whilethe pump sun gear 9 is still stationary, pumping action takes place andfluid is sucked from sump 36 by suctiontube 31 through 38 and 21 tovalve seat 30 and thence to inlet bores 2|, inlet ports ll, planet-gears8, and sun gear 8. As an oil fllled interstice of a tooth of gear 3mates with a tooth of gear 9, the fluid is forced through pump outletbore It and a motor inlet bore 20 to the fluid motor. The

sliding valve l8 within each bore I5 is positioned so that plunger I]does not engage bore 20; In themotor the flow is restricted in that suchbores 20 which empty into those portions of the motor gear cavity whichare blocked off bythe closed valves stop the flow as there is no outletfor it.

Thus in the position of the valves shown in Figure 3, with valves 45 and48 closed, hydraulic pressure is built up in the regions 63 and 64. Itwill be noted that such pressure on motor sun gear 39 is alsotransmittedto pump sun gear 9,

both of which are on the driven shaft 5. If this pressure is notrestrained by a load torque, the

motor gears must turn as there is no pressure in the altemateports and aturning moment is established which creates a torque. There is nopressure in the alternate ports as the valves 41 and 46 are fully opento the atmospheric pressure obtaining. within casing I. It will be notedthat the, direction of the turning moment is not dependent on thedirection of rotation of the driving shaft. As long as there is fiuidpressure in one or more tubular bores 20 connected to inter stices inthe motor that are blocked by the closed plungers i1 and pistons l8.Thus the centrifugal fiyweight action is at first counterbalanced byspring 3| and thereafter by the spring and the valves of the motor, thedriven shaft I can be rotated in either direction at will. Such bores 20as are not blocked by closed motor valves, are pumping fluid atnegligible pressure so that a minimum of'power is wasted. As the pumpand motor devices are integral mechanically, and the tubular bores inthe construction illustrated repfiuid pressure. The magnitudes of theseactions can be fixed by design to meet the torque and speed requirementsof the given prime mover and the load. Thus a pressure diflerentialbetween the pump and motor is created, and the vpower transmitted todriven shaft 8 is divided between them in accordance with the ratio oftheir displacements multiplied by the respective pressures on them. Asthese throttling plungers I! close the said passages 20, the pressure inthe motor rapidly becomes negligible and the torque load is assumed bythe pump mechanism. When the plungers completely restrict the flow tothe motor, and shafts 4 and I are rotationally inte'r I looked, a director 1:1 transmission results.

resent six separate and individual hydraulic systems, they actindividually in succession as their associated interstices passthrough-the high pressure valve areas. with they overlapping multipledesign as shown, there will thus be one or more tubular-bores in actionat any time. I

' If the torque created by the pressure overcomes I the load torque onthe driven shaft, the latter will rotate. In the valve setting of Figure3 the direction will be clockwise, and obviously w'ill be.

counter-clockwise if valves 48 and 41 are closed, and 45 and 48 opened.As the motor sun gear rotates the fluid passes out through the openvalves, through the upper and lower exhaust bores In the foregoingdescription I have used the term hydropu1se," which requires defining. Iemploy such term to distinguish atom of mechemical-hydraulic actionemployed in my invention from the hydrostatic and hydrodynamic.

types of such action. The difierences between and drops'into the sump,from whence it is recirculated. It will be noted that, by the relativerotation of the pump and motor housing. there results the intermittentconnectionof a pressure volume' in the pump to an exhaust port in themotor, whichwould have'the effect, were the mechanism not in multiple,of producingan intermittent transmission of power. However, the

so that at any point in rotation a'closed pressure system is created-byat least one of their combinations. As the fluid is incompressible, thetotal driving action is taken by such closed pressure combination, orcombinations, and the transmission vis continuous.

If the static, or rotating, load torque is greater than the drivingtorque multipled by the hydrostatic action conversion ratio as fixed bythe ratio of the volumetric displacements, the driving shaft 4 will slowdown. Flyweights 22 thus will not overcome spring action 32 to thesame-extent and piston 23 will move to the right to throttle the inletfluid flowing to the pump until the pump displacement is only partlyfilled, changing the action from hydrostatic to hydropulse conversionwhich gives increased torque ratios. The

throttling effect will increase until the torque created on the drivenshaft by the pump reaction, and the motor action, overcomes the loadtorque, at which point the action becomes steady. It the driving torqueis increased over the requirement,

- operating in such manner that the upper driving cylinder receives asupply of incompressible fluid action of. the pump and motor pinionsoverlap the system will tend to accelerate and the inlet valve 30 willopen until full volumetric discharge of the pump is in action. At thispoint the hydrostatic torque conversion will again take place. As

the speed increases the piston 23 moves further to the left, wherebyplate 35 pushes slide valves- Hi to the left and the throttling plungersthereof start to restrict the pump motor inlet passages 28. As, the flowis restricted the pressure in the piston chamber increases, and aresistance to the further leftward movement of the plungers I1. iscreated by the difierential pressure on the such hydropulse action fromeach-of the others,

and the application thereof in principle to trans- 1 missions, are bestexplained with the aid of Figures 6 to 8 inclusive.

In Figure 6A there is shown a schematic view of hydrostaticmechanical-hydraulic action.

Two rotatable shafts, each provided with a flywheel, have individualcrank and piston mechanisms, with the two'pistons working each in aseparate 'cylinderin the same housing. Between the displacement areas ofthe cylinders is a connecting line controlled by a valve mechanism 6|,indicatedschematically and comprising inlet and outlet valves to each ofthe connecting cylinders on its inlet stroke, passes such supply to thelower driven cylinder on its outlet stroke, and allows the lower drivencylinder to exhaust freely in the also be part of a multiple set ofcylinder mechamm in parallel with suitable phase displace- 4 ment oftheir reciprocating and rotating parts to insure continuous positivecoupling between the driving and driven shaita The torque exerted on thelower, driven or motor, shaft will be in proportion to the ratio of thedisplacements! the upper, or pump, cylinder to, that of the lower,

, or motor, cylinder. The speed 0! the motor shaft will be thereciprocal of such ratio. Y This is true 7 as the fiuid isincompressible andthe displacments are completely filledand the leakageof the schematic mechanisms is negligible. The hydrostatic (Figurednl-xtype of power transmission is particularly attentive where non-slipconditions are required between the driving and'the driven shafts. It isreadily capable oi handling large torques in small mechanisms, is quite'eiilcient at low speeds, and'particularly suited tor a 1:1 ratio drivein a diflerential mechanism in which the fluid becomes essentially astatic compression.

it may be.

member. Its principal limitation is that it is fixed at a given ratio.

In Figure 6B hydrodynamic torque conversion ing mechanism and isessentially the same-as the pumping mechanism of Figure 6A. The lower,or motor, mechanism is, however, diflferent in that it is not necessaryto restrain the'motor piston in the same housing as the pump piston,although Valve mechanism 02 of Figure 6B permits drawing the fluid intothe pump cylinder on the intake stroke and the ejection thereof throughan accelerating nozzle to impinge on the motor piston. By said nomle thehydraulic pressure energy created by the pump pistonis conrevolutiontorque action on the motor shaft will be maintained. 1 have shown thishydrodynamic principle by the schematic view of Figure 63 to keep itsillustration as analogous to that of hydrothe active exhaust stroke.

static conversion as possible, rather than repre= senting it by the moreusual centrifugal pump actuating a hydraulic turbine or water wheel. Itis to be noted that in the latter case the nozzle need not be presentbetween the driving (pump)? move with a speed of the order of magnitudeof the nozzle stream because the peak efiiciency of hydrodynamicmechanisms is obtained at conditions of low slip between the dynamicfluid stream and the mechanical element. Its main advantages are that bycomparatively simple valve ad- 'justments'the speed and torque ratiosmay be version.

varied, that latitude of design is allowed by the omission of a positivepressure housing structure between the driving and driven elements, andthat extraordinary shock impulses cannot be transmitted through it. i

In Figure SC I illustrate what I designate the hydro-pulse"mechanical-hydraulic torque con- The structure generallyis the same asthat of Figure 6A with only the basic difference that its valvemechanism 63 operates differently.

Valve 63 is so arranged that it does not permit the upper pump, ordriving, piston to draw through it suflicient fluid to completely flllthe entire pump piston displacement on the inlet stroke. The pump pistondisplacement is permitted to fill only partially, and for the greater[part of' its stroke the pump piston is out of contact with the fluid.As to the driven,'or motor, piston the action of valve 63 is the same asthat of valve 6| of Figure 6A, that is, as pressure is created by thepumping mechanism, 63 valves the fluid into the motor or drivenmechanism with the proper phasing to make the motor rotation continuous.Just as the pump mechanisms of .Figures 6A and 63, so also is that ofFigure 6C operated by a constant torque source of power, smoothed by aflywheel, which the pump shaft torque will attempt to acceleratecontinuously. However, in Figure 60 on the pump pistons intake stroke ithas soon drawn in its partial fluid charge and then, as'the fluid isinexpandable and incompressible, the pump piston for the balance of vits intake stroke will beopposed only by a negligible atmosphericpressure. On the return and discharge stroke, the pump piston for all ofits travel while out of contact with the fluid, and assisted byatmospheric pressure, will continue to accelerate and store rotationalenergy in the pump shaft flywheel. When the pump piston, on

the last part of its discharge stroke, engages the fluid the drivingtorque will attempt to maintain the same energy transfer conditions.- Ifthere is resisting pressure on the fluid suflicient to exceed the forceof the driving torque, the driving mechanism will not only be held'toconstant speed'but will be decelerated, the deceleration lasting duringAs soon as the exhaust stroke is over, the driving mechanism will againstart to accelerate. Steady state conditions will result when thedeceleration during the active portion of the cycle is equalized by theacceleration during the non-active portion. If the driving and thedriven torque be considered constant, any ratio between them can bematched by proportioning the amount of inlet fluid through the pumpmechanism. The hereinbe-.

fore hydropulse action is analogous to the action of a mechanical punchpress in. that energy, stored in a flywheel the greater portion of'acycle, is removed at extremely high forces during a small fraction ofthe cycle. Like the punch press, hydropulse action offers the advantageof exerting tremendous forces at slow over-all speeds by means ofrelatively low prime mover power. Its range may be varied through wideratios by very simple valve operations. By further valve operationshydropulse action, as shown, can be changed over to hydrostatic action.Power efliciencies of hydropulse action are-low compared to generalpower transmissions, but this is of little practicalefiect, for theexertion of large driven torques though necessary is the extraordinarycondition and their application is generally of short duration.Hydropulse action has both I positive and flexible control to meet suchconditions.

power transmission combining hydrostatic and hydropulse action. Drivingshaft I00, provided with flywheel ml, is integral with the centralelement I02 of a positive displacement pump of the eccentric cylinderand sliding vane type. Vane I03 is slidable radially in and out ofelement I02, a spring (not shown) constantly urging it outwardly intocontact with cylinder wall I04 within the housing I05. Valve I08 passesthe.

fluid through bore I09 to the fluid motor inlet In Figure 7 I disclose aschematic view of a portIII. 'rhe iiuidmotor is built into the sta-'tionary housing I I0, the cylindrical wall I I4 bein v eccentric to themotor rotor element I I0, which is integral with driven shaft I00. Motorvane I I2 is; similar in its construction and in its spring guidedradial motion to pump vane I00. Motor inlet port III is, however, a partof the rotatable central motor element Ill, and is so positioned,relative tovane I I2, as to admit the fluid supply pressure at all timesto the expanding volume in the motor. Motor outlet port I II isconnected by bore H8 in housing II! to fluid supply line I ll. Motorexhaust port I II is on the decreasing side of the motor cylinder sealclearance, so that the fluid in that volume can have no gauge pressure.External fluid line I" maybe too. pump,

or open to atmospheric pressure.

When driving shaft I is moved by a constant torque prime mover, notshown,pump vane I00 will rotate and in passing inlet port I01,positioned at a point of minimum clearance between the cylindricalsurface I02 and the cylindrical surface I04, a region of expandingvolume will be formed between such surfaces and the lagging sideof thevane. If now valve Ill be open to connect port I01 to the fluid supplylll this. expanding volume will be fllled'by fluid under atmosphericinduction (or with the aid of a pump not shown). In the meantime thevolume on the leading side of vane I03 is decreasingand the fluid insaid decreasing volume is forced out through exhaust pump port 0. Ifvalve I00 is wide open, and thus passing fluid with negligible impedanceto the flow, the pump vane will rotate as long as the torque of theprime mover can overcome the hydraulic pressure built up in the motorelement. The passed fluid travels into the expanding motor volume,through motor inlet a port III positioned as above stated, thus creatinga torquebetween housing 0 and driven shaft I06. Theoretically, thetorque produced in the motor is a function of the pressure transmittedfrom the pump element and is independent of the speed of the "drivenshaft.

The total torque on shaft I00 is the sum of that developed in the motorelement and the reaction on the pump housing I05 produced by the pumpelement. When the pump is operating with restriction at valve I00 thefluid pressure in the pum and motor must be equal. In any case, thefluid volume passing through the pump and the motor is identical. Thusthe ratio of 'the speed of the driven. shaft I06 relative to thetransmission housing I I3 to the speed of the driv ing shaft I00relative 'to the pump housing I05 is the ratio of the motor and pumpeffective displacements. Therefore the speed of the drivin shaft I00relative to the transmission housing I I3 I can be expressed as follows:

R. P. M. drive shaft==R. R M driven shaft Motor displacement Pumpdisplacement Neglecting friction and leakage, the fluid and mechanicalenergy has no other means of dissipation than the driven shaft I00, sotheoretically the power on the driving shaft I00 and the driven shaft I05 must be the same. on these shafts mu'st'be inversely proportional totheir speeds of rotation. From this it is seen that a theoreticallyinfinite torque multiplication can be effected by restricting the pumpinlet flow at valve II8, to decrease the effective displacement of thepump, and thus increase the ratio of the torque and the drivewill be 1:1ratio. Duringmotor displacement to the pump displacement. This is anillustration oi' the hydropulsc torque conversion appliedto adifferential hydraulic mechanism.

Consideration of the speed equation will show that as long as it holdsthe two shafts cannot have equal speeds unless the motor displacementbecomes infinitely smaller than the pump displacement. Practicalconsiderations mitigate against decreasing this below the ratio of thenew element is introduced by the action of valve I08. This restricts theflow out of the pump and puts a pressure differential between the pumpand motor. Thus the torque transmitted by the pump reaction isincreased. Conversely that created by the motor is decreased by a likeamount. Carried to the extreme, by closing valve I00 completely, thepump element will assume the entire the above changes the differentialfluid energy transmitted to the motor can be transformed by it intotorque, even with a non-expanding fluid. However, practical design ofsuch mechanism is difficult and the differential energy in such case isa very smallpercentage of the total, so that actual designs willprobably act as controlled slip mechanisms rather than true torqueconverters in this range. During these changes in torque and speed.conditions, the driven shaft will accelerate, or the driving shaftdecelerate, to come into synchronous speed with the other, the actualresults depending upon the load and the prime mover torque con-.ditions'. To assure smooth'action it is assumed that the'mass of theload on the driven shaft is sufficient to act as a flywheel on suchshaft, but if it is not, a flywheel is placed on said shaft I08.-

- While the displacement pump and motor of the sliding vane type abovedescribed are workable. their design possibilities are not as good asthose offered by the gear type rotary displacement pump, such as I haveshown in Figures 1 to 5, and hereinbefore described, and in my otherspecific construction shown in Figure 8 hereinafter described. The geartype rotary displacement pum is useful in hydraulic work over a widerange from vacuum to extreme high pressure systems. Consider two meshinggears with'incompressible fluid filling the interstices between thegear, teeth. Each gear, except where the teeth: of one mesh with theother, is enclosed by a .concentriccylindrical housing withflneclearance between it and the gear teeth tops, thus restraining thefluidradially as the gears rotate. The two housings, or, if a pluralityof gears mesh, then the plurality of housings, end at their mutualpoints of intersec- Hence the torque tion which is practically the pointof intersection of the addendum circles of the meshing gears. As a toothof one gear mates. with the interstice of the meshing gear, it projectsinto the interstice reducing its effective volume. Thusthe fluid must beforced out of the interstice, and fluid pressure will be createddepending on the restrictions, of the exhaust flow. As is known. portsmay be bored in the housing either at the point of the inter.- sectionformed by the housing cylinders, or in the end housing faces. Theseports are located so as to allow'the fluid under pressure to be forcedfrom the interstice. The fluid is prevented from flowing into thereceding interstlce by the fine clearance formed at the point of contactof the mating tooth faces. The fluid space .in a toothi'ntersticewillthus decrease until the center of the tooth interstice has passed thecenter line of the gear centers. Then the mating tooth will recedeand-the volume will increase, and if accurately designed this action canbe used to create a considerable vacuum. However, in most pumps thisaction is used to induce the fluid charge into the pump by atmosphericpressure. by providing ports on the inlet side of the pump positioned atthe im ge positions of theoutlet ports, and connecting fluid lines tothem as in the self-priming pumps. After filling the tooth interstice.the fluid is carried around the gear .tooth path until a mating tooth ofameshihg gear again enters it.

In knowngearpumps acommon fault, limiting their usefulness-andcausingthem to be subject to severe vibrationunderhigh speed and highpressure-conditions, is "trapping." As the mating lnterstlce approachesthe centerline of the gear centers, the leading contact is still formedand at thesame time a second point of contact is being formed rapidlybetween the back face of the mating tooth and the back face of the interstice. Thus the fluid between these two contacts is pped and must beforced through relatively small clearances. The hydraulic pressurescrease'meo whole transmission system. It will be particular lyv notedthat both the pump gears, 3 and 9, and

the motor gears 39, 40, and 4|, have overcome the trapping effect abovediscussed. As a tooth meshes with an oil filled interstice, the pressurebuilt up is relieved and the fluid exhausted through the tubular boresinthe driven shaft connecting with the radial bores in the interstices ofthe sun gears. Thus any fluid trapped at the top of a tooth and thebottom of an interstice is relieved without the above mentioneddestructive pressure and velocity conditions by the appropriate radialbores in the respective sun gears- In Figure 8, the driving shaft 230and the drivon shaft 23! are coupled by a triple planet pump mechanismof the type describedin detail above, essentially comprising sun gear232, pump planets 234, and planet housing 235 integral with the drivenshaft, and havinglclearance on the inlet side of the pump planets, Theflexible fluid sup- 7 ply line 235 connects to the sleeve type slidevalve mechanism 231 and the latter in turn to supply bore 238 and theclearance inlet slots around the pump planets, as hereinbefore describedin detail in connection with Figure 2'.

, bores 239 in the driving shaft are adapted to receive pumped fluidfrom an end of the individual .ated under such conditions frequentlyspring sub- 'stantial pump shaftsanddamagebearings. The fluid speeds,will wire-draw); the sides of the fln'e clearance much the sameas,:they. will in faulty .high pressure valves. The-action of the fluidbeing forced through the orifice will tend to break down the chemicalstructure of organic fluids, such as oils, causing them. tobe unsuitedto the operation. So also the .lntense tooth pressure between the gearswill cause "brinelling of their 7 surfaces ruining the tooth form. Thefluid forced from the trapped area generally passes through ,the leadingclearance as-there is l'ess resisting pressure in this direction, thuspartially filling theexpandin volume and reducing pump efllciency, Tominimizetrappin'g. most pumps are designed with. wide clearances orwithoverlapping ports,=-considerabiy decreasing pump efllciency,

The gear pump structure is also used as a ydraulic motor. As it isself-valving and has a positive-displacement action, it will be seenthat if fluid pressureis admitted to the ports on one side. and theother side is vented freely to the atmosphere'or to-r'educ'ed pressure.the gears will Agate 'unIess-restrainedby a torque great enough toovercome the inlet-outlet pressure differential.

The advantage or such a motor is that it can be designed to providepositive non-,overrunning.

movement. Its disadvantag is that trapping occurs where thegears mesh'unless ineflicient clearances or ports areprovided.

The ordinary gear pump structure consists of two gears meshing atonelpoint. While such a 1 gear pump can be designed into my variablespeed transmissions-I prefer the use of structures having one centraLorsun. gear mating with wo,

. three.,or more, other or planet. gears. It wi be noted that thehydraulic .motor of-Figure 1 comprises a 'sun., '-,gear with.twoplanets, while the Pump'oi Figure 1 comprises a sun gear with threeplanets. These multiple arrangements oifer balanced conditions on thesun gear bearings and the possibilityof minimizing resonant impulses b'tween'these and with other elements of the sun gear tooth interstices. Ican also employ sun gears with radial'bores connecting to theinterstices and the bores parall'el to the shaft axis, as I have used inthe transmission of Figure 1. Individual bores 239 terminate in a seriesof radial nozzles 240 adapted to direct their'fluid streams againstvanes 24l of hydraulic reaction turbine integral with driving shaft 230.Thrust bearing 248 compensates for the interstices end pressure thrustbetween the driving and driven shafts. Control mechanism 249 is splinedto the driving shaft so that it revolves with it but is free to movelaterally along it. It comprises a sleeve 243 adapted to cover anduncover nozzles 239, and a gear 244 rigidly connected to a flyweight 242pivoted to the sleeve. meshes with rack 250 out into the driving shaft.Motion of the sleeve .243 caused by the fiyweight and the .rack and gearis opposed by biasing spring 245 which normally keeps sleeve 243 in theposition where all nozzles 239 are uncovered. Sleeve 243 also carries acircular thrust face 25.4 on which rides the short end of lever 25L.This lever 2U is pivoted around flxed pin 255 and is held in placeagainst face 254 by spring 256 and link 251. The force on spring 258 istransmitted toarm 253 which isintegral with supply sleeve 231. Thesupply sleeve 231 is pulled to the left by spring 253 which is weakerthan the sprin 253 so that it does not act until the latter is fullyrelieved. By this arrangement, when valve 243 has fully uncovered thenozzles, further movement thereof to the right moves inlet valve 231 tothe left and restricts the flow of inlet fluid to the pump. Shaft 2 30is stepped at 252 to permit the formation between it and sleeve 243 ofan annular chamber 243, to which fluid is admitted from tubular bore 239by the restricted passage 253. Fluid to the annular chamber may be ob-'tained from any one of the tubular bores or from them all in parallel ifthe passages 253 are sufliciently restricted to prevent more thannegligible fluid power passing between them.

Individual Gear 244 uncovered nozzles 240. The streams from the nozzlesimpinge against the'turbine vanes 24l where their reaction deceleratesthe velocity of the fluid and converts the energy into a rotationalreaction torque in the direction of rotation of the mechanism, the spentfluid falling into the supply sump, not shown. This reaction torqueeffectively increases the driving shaft torque, and thus an increasedtorque is transmitted to the driven shaft. As the outlet nozzles aredirected radially, they produce no useful force from the reaction of thefluid acceleration. As the centrifugal force increases, it movesfiyweight 242 and gear 244 against the biasing spring 245 and the fluidpressure in the annular chamber 243,-moving sleeve 243 over the nozzles,to the left in the figure. When the nozzles are blocked there is nofluid ejected, hence no slip, and the drive is direct, fluid beinginducted into the pump mechanism to fill it completely. When the speeddecreases, and the centrifugal force becomes less, or the torquetransmitted becomes greater, fluid pressure in the annular controlchamber 248 overcomes the centrifugal force and sleeve 243 slides to.the right, uncovering the nozzles. This permits the discharge of fluidfrom the pump, a1- lowing slip between the driving and driven shafts andcreating additional torque on the driving shaft by means of hydrodynamicaction. But as valve 243 moves to the right, the reversing linkage movesthe sleeve 231 to the left, restricting the fluid inlet flow to thepump, sleeve 231 registering only partially with fluid supply bore 238.Thus hydropulse action results, increasing the torque conversion andovercoming the overload causing the decreased shaft speed. As aresult,sliding valve 243 will automatically'adlust the rate of flow until it isbalanced and a steady state of conversion has been reached. Biasinspring 245 is included in the mechanism as it aeeaeso I uncovers thenozzles at low rotational speeds,

thus relievingany hydraulic pressure and preventing the transmission ofany torque so'that the driving shaft may idle at low speeds.

The main advantage of the structure of Figure 8 over that of Figure 1 isthat when the present structure is running normally with a straight 1:1transmission, no idling parts of the hydraulic turbine (vanes 2 4I)operate, resulting in a minimum power waste during normal running. I

Although I have shown and described certain specific embodiments of myinvention, I am fully aware that many modifications are possible. Myinvention, therefore, is not to be restricted ex- I cept in so far as isnecessitated by the prior art and by the spirit of the appended claims.

What I claim is:

'1. In a hydraulic power transmission, a driving shaft, a driven shaft,intermeshed gearin coupling said shafts, a fiuidconfining housinenclosing. said gearing, a passage for conducting fluid into saidhousing, a second fluid passage -in and through said gearing throughwhich fluid is propelled by said gearing to externally of said housing,a hydraulic motor external to said housing and adaptedto be driven bythe propelled fluid emitted from said second passage, and means withinsaid second passage operatable by centrifugal force to restrictprogressively the emitted fluid from a predetermined maximum down tozero as determined by the speed of the driving shaft and theload on thedriven shaft.

v.2. In a power transmission, a drivingshaft, a casing integral withsaid shaft and having a flywheel effect, a' positive displacementhydraulic pump member on said driving shaft and within said casing, apas age for fluid from the exterior of said casing to the interiorthereof,

a driven shaft extending into said casing, a sec in and throughsaidsecond pump member and to said fluid motor means, restricting meanswithin said second passage for regulating the quantity and rate of fluidflow, and driving shaft speed control means for operating saidrestricting means.

3. A hydraulic differential :torque converter 2 comprising a drivingshaft rotatable in a predetermined direction, an enclosing gear carrierrigid on such shaft and having appreciable mass, a plurality of planetgears rotatably'supported in said gear carrier, a plurality of recessesin said gear'carrier each concentric with an in dividual planet gear, apassage for fluid within said gear carrier having ports in each saidrecess, a valve in said passage centrifugally operatable by said gearcarrier to regulate the amount of fluid introduced into the passage, adriven shaft centrally disposed in said gear carrier and extendingtherebeyond, a sun gear rigidly on said driven shaft on the portionthereof within the gear carrier and meshing with said planet gears, arecess in said gear carrier concentric with the sun gear and havingminimum clearance therewith, the recesses for the planet gears havingappreciable clearance from their respective gears for the greaterportion including the fluid port region and minimum clearance shortlybe-' fore and at the region of engagement of the teeth of theirrespective planet gears with those of the sun gear, a plurality ofradial port groups spaced about saidsun gear, an axial bore in said.driven shaft for each of said radial port groups and connectingthereto, a valve in each said axialbore and. centrifugally operatable bythe rotation of said gear carrier to control the passage of fluidthrough said axial bores, a second sun gear on said driven shaft on theportion thereof extending externally of said gear carrier, a pluralityof radial port groups spaced about said second sun gear and in phasecorresponding to the port groups of the first sun gear, each said portgroup being connected to the axial bore of the corresponding group inthe first sun gear,

a plurality of gears engaging said second sun gear, a fixed enclosinghousing about said second sun gear and its engaging gears, the interiorof said housing having minimum clearance therethepredetermined directionor in the direction opposite thereto. a

4. A differential torque converter with hydraulic action, comprisingadriving shaft, .a casing integral with the driving shaft, a drivenshaft, a first hydraulic pumpielement integral with the. driving shaft,a secondhydraulic pump element integral with the driven shaft andcoacting withsaid first hydraulic pump elementboth pump elements beingenclosed in said vcasing, a hydraulic supply line to said pump elements,means in said hydraulic supply line for restricting the .fiow of fiuidtherein, a rotatable motor element integral with the driven shaft 8 andpositioned externally of said casing, a hydraulic output line from saidpump elementsto said rotatable motor element, and valve means in saidhydraulic output linecontrollin the flow of fiuid tosaid rotatable motorelement.

5.'A hydraulic differential torque converter an inlet for fluid from thereservoir into niecesing to the first pump member, a valve in the inlet,

for fluid in and through said pump member into. 7

said hydraulic motor means, a second restricting j means within saidsecond passage for regulating the fluid flow from a maximum to zero, afluid exhaust from said motor means, and means for simultaneouslyoperating both said restricting means so that the restricting means inthe first passage opens the first passage while the second restrictingmeans in the second passage closes the second passage. a

6. A differential torque converter with hydraulic action comprising adriving shaft, an enlarged .portion having a flywheel integraltherewith, a first hydraulic pump element integral with said drivingshaft, a driven shaft, a second hydraulic pump element integral'with thedriven shaft and coacting with said first hydraulic pump element, ahydraulic supply. line to said pump elements, valve means forcontrolling the flow of fluid in said supply line, a hydraulic motorincluding a rotatable element integral with said driven shaft, ahydraulic output line from the second pump element to the rotatablemotor element, a fluid exhaust from the motor, a second valve means inthe output line interconnected with the valve means .in the supply line,and means controlling both valve means so that onoperation of the valvemeans in the supply line toward full opening of the'supply line thesecondvalve means is simultaneously operated toward closure of theoutput line.

7. A differential hydraulic torque converter comprising a first shaft, acasing integral with the first shaft and having a flywheel effect, apositive displacement hydraulic pump member on the first shaft withinthe casing, a second shaft extending into the casing, arsecond pump.

member on the second shaft coacting with the positive displacement pumpmember and also within the casing, a hydraulic motor including arotatable element integral with the second shaft, a reservoir for fluid,a hydraulic line from the reservoir to the positive displacement memberto and through the second pump member to and through the rotatable motorelement through the motor and back to the reservoir, valving means.

in the hydraulic line, and means controlled by the speed of one of theshafts for actuating the valving means.

8. A differential torque converter with hydraulic action comprising afirst shaft, a casing on thefirst shaft and having a flywheel effect, afirst hydraulic pump member on the first shaft within the casingyasecond shaft extending into the easing, a second hydraulic pump memberon the second shaft within the casing and cooperating with the firstpump member, a reservoir for fluid,

housing on the driven shaft,'a fluid passage for means, an exhaustpassage for fluid from the a hydraulic motor including a rotatable motorelement integral with the second shaft exterior to the casing, ahydraulic line from the second the casing, a second shaft extending intothe casing, a second hydraulic pump member on the second shaft withinthe casing and cooperating with the first pump membeiga reservoir forfluid, an inlet for fluid from the reservoir into the casing to thefirst pump member, a valve in the inlet, a hydraulic motor including arotatable motor element integral with the second shaft exterior thecasing, a hydraulic line from the second pump member through therotatable motor element into the motor, a second valve in the hydraulicline, a hydraulic exhaust from the motor, and means controlled by thespeed of one of the shaftsfor actuating both valves simultaneously withthe inlet valve moving toward the full open inlet position and thesecond valve moving toward closure of the hydraulic line with increasingshaft speed.

10. A hydraulic differential torque converter comprising a drivingshaft, .2. flywheel on the driving shaft, a positive displacementhydraulic pump member on the driving shaft, a fluid reservoir, a housingenclosing the displacement pump member, an intake for fluid from thereservoir into the housing and to the pump member, restrictin means inthe intake for regulating the fluid flow from zero to a maximum, adriven shaft extending into the housing, a second pump member on thedriven shaft within the housing and cooperating with the positivedisplacement hydraulic pump member, fluid motor means exterior to theconducting fluid from the second pump member to the hydraulic motormeans, an exhaust for fluid from the motor means to the reservoir, anddriving shaft speed control means for operating the restricting meanstowards maximum 'flow in the intake .with increasing driving shaftspeed.

11. A differential hydraulic torque converter comprising a drivingshaft, a casing integral with the driving shaft and having a. flywheeleffect. a positive displacement hydraulic pump member on the drivingshaft within the casing, a first passage for fluid from the exterior ofthe casing to the pump member, a valve within the fluid passage, adriven shaft extending into the casing, a second pump member on thedriven shaft cooperating with the positive displacement hydraulic pumpmember, fluid motor means exterior to the casing on said driven shaft, asecond fluid passage through the second pump member into the motor motormeans, and driving shaft speed control means for progressively operatingthe valve from closure to full opening of the first fluid passage withincreasing speed of the driving shaft.

12. A differential hydraulic torque converter in accordance with claim11, characterised by a second valve in the second fluid passage, valveopening means tending to retain the second valve in the position inwhich the second passage is full the second fiuid passage withincreasing driving shaft speed so that the second valve closes thesecond passage at a predetermined speed.

13. A hydraulic differential torque converter comprising a housing, adriving shaft, a flywheel on the driving shaft, a positive displacementhy-.

draulic member on the driving shaft, a casing enclosing the positivedisplacement hydraulic memher, a passage for fluid from the interior ofthe housing to the interior of the casing and the hydraulic member,restricting means within the passage for regulatingthe fluid flow fromzero to a maximum, a driven shaft, a pump member on the driven shaftcooperating with the hydraulic member and within the casing, a. motormember on the driven shaft exterior.to the casing and within thehousing, a second positive displacement hydraulic member on the housingcooperating with the motor member, a second fluid passage in and throughthe pump member, the driven shaft and the motor member to the secondpositive displacement hydraulic member, an exhaust passage for fluidfrom the region of cooperation of the motor member and the secondpositive displacement hydraulic member into the housing, a secondrestricting means within the second fluid passage, and driving shaftspeed control means for operating the first restricting means fromclosure to full opening of the passage while operating the secondrestricting means from full opening to closure of the second passagewith increasi cg speed of the driving shaft.

14. A differential torque converter comprising I a driring shaft, ahousing of appreciable mass on the driving shaft, a first recess in thehousing, a first rotatable positive displacement hydraulic pump elementsupported within and substantially filling the first recess, a secondrecess in thehousing connecting with the first recess, a driven shaftextending into the second recess, a second rotatable pisitivedisplacement hydraulic pump element c n the driven shaft within andsubstantially filling the second recess andengaging with the firstrotatable positive displacement hydraulic pump element, a fiuid passagefrom without the housing into the first recess at a region remote fromthe engagement of the first and second rotatable positive displacementhydraulic pump ele ments, a valve in the fluid passage, valve closurevmeans tending to retain the valve in its passage closing position, aplurality of fluid ports spaced around the second rotatable positivedisplacement hydraulic pump element extending therethrough into thedriven shaft with each port independent of and hydraulically sealed fromeach other port, an axial bore in the driven shaft for each port andconnecting with the particular port, a third rotatable positivedisplacement hydraulic element on the driven shaft exteriorto thehousing, a second plurality of fluid ports spaced around the thirdrotatable positive displacement hydraulic element extending therethroughinto the driven shaft, the ports being independent of and hydraulicallysealed from each other port in the third rotatable positive displacementhydraulic element with the individual ports connecting each with anindividual axial bore, a fixed housing, a first recess in the fixedhousing enclosing and substantially filled by the third rotatablepositive displacement hydraulic element, a second recess in the fixedhousing connecting with the first fixed housing recess, a fourthrotatable positive dia- 9 placement hydraulic element in the secondfixed housing recess eng ing with the third rotatable positivedisplacement hydraulic element and substantially filling the secondfixed housing recess, I

hydraulic elements and extending into the second fixed housing recess inthe region of its connection to the first fixed housing recess, meansfor blocking one exhaust port and unblocking the other exhaust port, andmeans controlled by the speed of the driving shaft progressively toactuate the valve against the valve closure means on increasing drivingshaft speed to the fully open position of the passage at a predetermineddriving shaft speed. 7

15. .A differential hydraulic torque converter comprising a drivingshaft, a housing of appreciable mass onthe driving shaft, a first recessin the housing, a first rotatable hydraulic pump element supportedwithin and substantially filling the first recess, a second recess inthe housing connecting with'the first recess, a driven spaced around thesecond rotatable hydraulic pump element extending ,therethrough intothedriven shaft with each port independent of and hydraulically sealed fromeach other port, an

axial bore in the driven shaft for each port and connecting with theparticular port, a valve positioned within each axial bore, valveclosure means tending to retain the fluid passage valve in its passageclosing position and tending to retain each axial bore valve in the borefull open position, a third rotatable hydraulic motor element on thedriven shaft exterior to the housing, a

second plurality of fluid ports spaced around the third rotatablehydraulic motor element extenddraulic motor element with the individualport connecting with an axial bore, a fixed housing. a first recess inthe fixed housing enclosing and substantially filled by the thirdrotatable hydraulic motor element, a second recess in the fixed housingconnecting with the first fixed housing recess, a fourth rotatablehydraulic motor element in the second fixed recess engaging with thethird rotatable hydraulic motor element and substantially filling thesecond fixed housing recess, an exhaust port in the fixed housing toeach side of the plane of the region of engagement of the third andfourth rotatable hydraulic motor elements and extending into the secondfixed housing recess in the region of its connection to the first fixedhousing recess, means for blocking one exhaust port and unblocking theother ex haust port, and means controlled by the speed ofthe drivingshaft progressively to actuate the fluid passage valve with increasingdriving shaft speed to the fully open position of the passage at apredetermined driving shaft speed and simultaneously actuating the axialbore valves so that at a second predetermined lower driving shaft speedthe axial bores are each partially restricted v v v and are whollyclosed at thepredetermined driving shaft speed; Y 1 4 16. A diflerentialtorque converter {with hydraulic actioncomprising a housing. adriving'shaft, a drivenshaft, a first hydraulic pump ele-,

ment integral with the driving shaft, elsecond' casing -enclosing thepump elements. the pump elements each forming with; the casing aplurality of positive hydraulic displacement units. a fluid supplypassage to theilrst pump element,

' a first hydraulic motor element on the driven hydraulic pump elementintegral with the driven? vshaft-coacting with the first pump element, a

shaft exterior to the casing and enclosed by the housing, a secondhydraulic motor element sup-g ported on and enclosed bythe'lmusingthemotor elements each fo'rming-with' the housing a plui rality of positivehydraulic displacement units, a

asa'mso shaft speed is attained.

19. A hydraulic torque converter comprisinga driving shaft, a housingintegral with the driv ing shaft, a'first recess in the driving shafthous ing, a fluid intake passage from without the housing into therecess, a first gear rotatably supported within the recess, the upperends of the gear teeth forming hydraullc'seals with the recess wallsfora region extending over several gear teeth, a second recess in thedriving shaft housbranch fluid passage from eachdisplacementunit of thesecond pump element to adiflerent one of the displacement units of thefirst motor element, a fluid outlet passage on either side of ingconnecting with thefirst recess. a driven shaft, 9. second gear on thedriven shaft within the second recess in engagement with the firsttheplane of engagement of the first and second motor elements andadjacent to such engagementregion, and means-in the outlet passages toblock those displacement units of the motor elements connecting at thetime with the one outlet passage: and simultaneously to relieve those ofthe other displacement units of the motor ele ments connecting at thetime with the other outlet passage.

17. A hydraulic torque converter comprising a driving shaft, a houslngonthe driving shaft, 9. first recess in the housing, a first rotatablehydraulic pump element supported within and substantially filling thefirst recess, a second recess in the housing connecting with the firstrecess, a driven shaft extending intothe second recess. a secondrotatable hydraulic pump element on the driven shaft within andsubstantially filling the second recess and engaging with thefirstrotatable hydraulic pump element, a fluid passage from without thehousing into the first recess at a region remote from the engagement oithe first and second rotatable hydraulic pump elements, a plurality offluid ports spaced around the second rotatable hydraulic pump element extending therethrough into the driven shaft with each port independent ofand hydraulically sealed from each other port, an axial bore in thedriven shaft for each port and connecting to the par ticular port, athird rotatable hydraulic motor element on the driven shaft exterior tothe housing, a second plurality of fluid ports spaced around the thirdrotatable hydraulic motor element extending therethrough into the drivenshaft, the ports being independent of and hydraulically sealed from eachother port in the third rotatable hydraulic motor element with theindividual port connecting with an axial here, a fixed housing, a firstrecess in the fixed housing vide a port inithe tooth interstices of thethird enclosing and substantially filled by the third rotatablehydraulic motor element, a second resees in the fixed housing connectingwith the first fixed housing recess, a fourth rotatable hy extendinginto the second fixed housing recem in. the region oi its connection tothe first fined housing recess, and means for blocking one exgear',theupper ends of the second gear formlng hydraulic seals with the walls ofthe second recess except for the region in which the two recessesinterconnect andln which the first and second gears-engage, a fluid portin the mascot each tooth interstice oi the second gear extending intothe driven shaft, an axial bore in the driven shaft for each fiuid portin the second gear and connecting with the individual port, a

fixed housing, a first recess in the fixed housing, a second recess inthe fixed. housing connecting with the first fixed housing recess, athird gear on the driven shaft exterior the driving shaft housing with asufllcient number of teeth to progear for each port in the second gear,the first fixed housing recess enclosing the third gear so that. theupper ends ofthe teeth of the third gear form hydraulic seals with thewalls of the first fixed housing recess except in the immedi: ate regionor interconnection of the first and second fixed housing recesses, aport positioned in thetooth interstices of the third gear for each axialbore, each port being individual to and connecting with one axial bore,a fourth gear rotatably supported on the fixed housing within the secondfixed housing recess and engaging the third gear. the upper ends oi theteeth of the fourth gear forming hydraulic seals with the walls of thesecond fixed housing recess except in the immediate region of theengagement of the third and, fourth gears, a fiuid exhaust passage toeach side ofthe plane of engagement of the third and fourth gears and inthe region of interconnection of they first and second fixed housingrecesses to exterior the fixed housing. and means for blocking oneexhaust port while relieving the other exhaust port whereby on rotationof the driving shaft and the flow of fluid through the intake passageinto the first driving a shaft housing recess into the tooth intersticesof the first gear to and into the tooth interstices of the second gearinto the fiuid ports of the second gear through theaxial bores to theinterstices of the third gear and to the tooth interstices of the fourthgear, those of the fluid paths so determined for the period of thepassage of their respective termination at the fourth gear into andthrough the relieved exhaust port are pressureless while simultaneouslythe other of the fluid paths sodetermined transmit hydrau lie pressureto the fourth gear.

' DICK Ems FU'ELZQRTON. JR.

